IF-combined smRNA FISH reveals interaction of MCPIP1 protein with IER3 mRNA

Area of Science:

• Molecular Biology
• Immunology
• Gene Regulation

Background:

• Monocyte chemoattractant protein-induced protein 1 (MCPIP1) is an RNase crucial for controlling inflammation-related mRNAs.
• Immune homeostasis relies on proteins like MCPIP1 and IER3, which regulates apoptosis and protects immune cells.
• MCPIP1 degrades stem-loop-containing mRNAs, including IL-6, influencing inflammatory responses.

Purpose of the Study:

• To investigate the role of MCPIP1 in regulating IER3 mRNA levels.
• To identify the mechanism by which MCPIP1 affects IER3 mRNA stability.
• To explore the functional consequences of MCPIP1-IER3 interaction in immune regulation.

Main Methods:

• Dual luciferase assay to assess MCPIP1's effect on IER3 3'UTR activity.
• Sequence analysis and structural examination of IER3 3'UTR to identify regulatory elements.
• Immunofluorescence-combined single-molecule RNA FISH to visualize MCPIP1 and IER3 mRNA co-localization.
• RNA immunoprecipitation to confirm in vivo interaction between MCPIP1 and IER3 transcripts.

Main Results:

• MCPIP1 overexpression decreased luciferase activity linked to IER3 3'UTR, indicating regulation.
• A stem-loop structure within IER3 3'UTR, similar to that in IL-6 mRNA, was identified as a target for MCPIP1.
• Deletion of this stem-loop element abolished MCPIP1-mediated regulation of IER3 mRNA.
• MCPIP1 protein co-localized with IER3 mRNA, and its functional domain correlated with decreased IER3 mRNA levels.

Conclusions:

• MCPIP1 directly regulates IER3 mRNA levels by targeting a specific stem-loop structure in its 3'UTR.
• This interaction is crucial for controlling IER3 expression and likely contributes to immune homeostasis.
• The findings reveal a novel mechanism of gene regulation by MCPIP1 impacting immune cell function.